Integrated circuit fabrication generally consists of a series of process steps or stages, for example, photolithography, etch, strip, diffusion, ion implantation, deposition, and chemical mechanical planarization (also known as chemical mechanical polishing, or xe2x80x9cCMPxe2x80x9d). At each step or stage, inspections and measurements are conducted to monitor the equipment which performs the process as well as the overall process, individual processes, and interaction and integration among individual processes.
Typically supporting the integrated circuit fabrication process is a complex infrastructure of, for example, materials supply, waste treatment, support, logistics and automation. Integrated circuit fabrication processes tend to utilize one of the cleanest environments in the world.
Integrated circuits are typically made on or in a semiconductor substrate that is commonly known as a wafer. A wafer is a substantially round, thin disk, having diameters such as four inches to twelve inches, and thicknesses in the range of two to three quarters of a millimeter. During the fabrication process, materials or layers are added, treated and/or patterned on or in the wafer to form the integrated circuits.
With reference to FIG. 1, the equipment employed to fabricate integrated circuits may be classified, in a functional manner, into two categories:
Processing equipment (xe2x80x9cPExe2x80x9d): this type of equipment creates physical or chemical changes to a wafer; for example, equipment used in performing photolithography, etch, strip, diffusion, ion implantation, deposition and/or chemical mechanical polishing (xe2x80x9cCMPxe2x80x9d).
Monitoring equipment (xe2x80x9cMExe2x80x9d): this type of equipment measures and/or analyzes certain parameters on a processed product or test wafer in order to, among other things, ensure the process(es) has behaved according to specification. That is, MEs measure, evaluate and/or analyze the integrity of the process(es). For example, MEs include equipment used in conducting defect inspection, surface profiling, optical or other types of microscopy. Notably, certain MEs may cause or require changes to measurement sample wafers. For example, an SEM may require a measurement sample wafer be cross-sectioned in order to analyze its profile. Indeed, these samples may be special test wafers, instead of product wafers.
Generally, conventional monitoring equipment consists of the following subsystems or components:
1. Source unitsxe2x80x94i.e., units that generate and direct the technique and mechanism of interrogation (for example, electromagnetic wave, charged particles, electrical voltages and currents, etc.) towards the measurement sample wafer. The technique of interrogation depends on the parameter being measured. For example, when measuring the smallest feature sizes made on an integrated circuit, known as Critical Dimension (xe2x80x9cCDxe2x80x9d), an electron beam may be used to resolve features as small as those used in integrated circuit manufacturing.
2. Sensing unitsxe2x80x94i.e., devices or circuitry that samples, senses, detects and/or measures the response of the measurement sample to the interrogation from/by the source unit. The sensing units may include, for example, temperature, light sensors, image sensors, charged particle sensors, voltage and current meters, and/or detectors. In the example of measuring CD using SEM, the electron beam reflected or scattered from the wafer is collected to form a high-resolution image of the features or profile on the wafer surface.
3. Analysis and user interface unitsxe2x80x94i.e., units that rely on a general purpose or specialized computer, algorithms and software to analyze information collected by the sensing units and present the results in a suitable format to, for example, process engineers or higher-level yield management and analysis software.
4. Wafer handling unitsxe2x80x94i.e., units that are responsible for handling the measurement samples, most likely in the wafer format, including, for example, loading, unloading, aligning, and conditioning wafers.
Given the number of different parameters that are measured or inspected in assessing the integrity of a process, there are many different types of MEs employed in a typical semiconductor manufacturing facility. The MEs may utilize different physical principles to detect, inspect or measure one or more parameters that may be used to characterize the process. For example, thin-film thickness measurement tools measure the thin films deposited on the wafer utilizing, for example, ellipsometry, reflectometry, or sheet resistance.
There are many inventions described and illustrated herein. In one aspect, the present invention embeds some or all of the functionalities and capabilities of one, some or all of MEs in a wafer or wafer-like object. In the present invention, the wafer or wafer-like object has the capability to sense, sample, analyze, memorize and/or communicate its status and/or experience.
These active capabilities may be implemented in various different ways. In one embodiment, the xe2x80x9cactivexe2x80x9d wafer or wafer-like object according to the present invention may be disposed in a PE in substantially the same manner that a product wafer is sent into the same PE. The PE may process the xe2x80x9cactivexe2x80x9d wafer or wafer-like object in the same or substantially the same manner as it would process a typical product wafer. Moreover, the xe2x80x9cactivexe2x80x9d wafer or wafer-like object may exit the PE in the same or in substantially the same manner as a product wafer. The xe2x80x9cactivexe2x80x9d wafer or wafer-like object is referred to herein as an Equipment-in-Wafer (xe2x80x9cEIWxe2x80x9d).
In certain embodiments of the present invention, after the EIW exits the PE, it may be powered on or enabled to sense, sample, determine and/or provide certain parameters associated with the change(s) or modification(s) made to the EIW as a result of the previous process(es) (for example a deposition process). In addition, the EIW may analyze the effects of that processing, memorize and/or communicate information representative thereof to a processing unit (for example, a general purpose computer). For example, if an EIW is disposed in a PE implementing a chemical vapor deposition (xe2x80x9cCVDxe2x80x9d) process and xe2x80x9cexperiencesxe2x80x9d that process, after the EIW is removed from the PE, the EIW may sense, sample, analyze, memorize and/or communicate the thickness of the layer deposited by the CVD process at one, some or multi-locations on the surface of the EIW. This information may be used to determine whether the CVD PE is performing properly, in specification or out of specification, and how and where it was in or out of specification. In this way, the EIW is providing, among other things, the functionality and capability of an ME that is designed to measure the thickness of the same CVD deposition layer.
In certain embodiments, the EIWs may perform its function while undergoing a given process within the PE. In this regard, the EIW may sense, sample, measure, detect, analyze, memorize and/or communicate its xe2x80x9cexperiencexe2x80x9d (i.e., the sampled, measured, detected and/or analyzed information) during the process step or stage, which may be the same or substantially the same as that experienced by a product wafer. For example, where the EIW is disposed in a PE performing a CVD process, the EIW may sense, sample, measure and/or detect the thickness of the deposited layer at one, some or all of locations on the substrate of the EIW. The EIW may sense, sample, measure and/or detect that thickness at one instance, at a plurality of predetermined or various points in time, or continuously throughout the process.
The EIW may also memorize the information and/or communicate that information externally (via, for example, wireless transmission techniques) for detailed analysis by, for example, a computer and/or the PE. This information may be employed to determine whether, for example, the CVD PE is working in specification or out of specification.
In one aspect, the present invention is a device, system and technique to shrink or reduce one, some or all ME into an EIW having suitable circuitry, structures, materials, capabilities and/or intelligence to perform one or some or all of those functions currently performed by conventional ME. In this way, capital equipment of at least part of the industry""s infrastructure is reduced, minimized, and/or effectively or practically eliminated.
The EIW of the present invention may provide one, some or all of the following advantages:
In-situ, holistic system-level monitoring. In this regard, the EIWs may sense and/or memorize and/or communicate while the process is taking place, the process information collected is in-situ. Time-sequence recording. The process information may be collected at different time points during the process, thus it is possible to record the time-sequence of events.
Real-time or near real-time feedback. In certain embodiments, EIWs may collect information as the process is taking place and the information may be analyzed, in real-time, and provided to the PE, in real-time, for adjustment of process conditions to enhance and/or optimize the process results.
Seamless integration with many existing PE infrastructure. Since many PEs are designed to handle and process product wafers or other product substrates, and EIWs are made to have the same or substantially the same form factor, weight, and other mechanical and physical characteristics as a product wafer or product substrate, the introduction of EIWs in the manufacturing flow will often cause minimal changes, if any, to the existing manufacturing infrastructure.
Again, there are many inventions described and illustrated herein. This Summary is not exhaustive of the scope of the present invention. Moreover, this Summary is not intended to be limiting of the invention and should not be interpreted in that manner. While certain embodiments, features, attributes and advantages of the inventions have been described here, it should be understood that many others, as well as different and/or similar embodiments, features, attributes and/or advantages of the present inventions, which are apparent from the description, illustrations and claims xe2x80x94all of which follow.